In many conventional printing apparatuses, such as inkjet printers, a pen carriage is moved relative to the print medium to perform printing. The carriage carries one or more ink cartridges (called “pen” by those in the art), which eject ink drops onto the print medium during printing. Typically, the carriage glides (or “scans”) back and forth on a carriage rod that is mounted substantially orthogonal to the moving direction of the print medium. Some inkjet printers further include an anti-rotation mechanism to limit the rotational movement of the carriage about the carriage rod axis. One known anti-rotation mechanism is in the form of an anti-rotational roller mounted under the front end of the carriage. This type of roller runs along a track surface below the carriage during printing to prevent the carriage from rotating about the guide rod axis.
Another anti-rotation mechanism is in the form of an elongated guide or rail arranged parallel to the guide rod and adjacent to a distal end of the carriage. In inkjet printing, it is important that the carriage glides smoothly along the guide rod with minimum vibration so that ink dots can be accurately placed on the print medium. As printing speed increases, the tendency for the carriage to rock about the guide rod increases. The prior art anti-rotation mechanisms are not sufficient to prevent uncontrolled rocking of the carriage during high-speed printing, e.g. at 60 ips or more. There exists a need for a carriage system with mechanisms that are low-cost yet effective for stabilizing the carriage dynamics during printing, especially during high-speed printing.